In the recent years, several broadband wireless technologies have been developed to meet the growing number of broadband subscribers and to provide more and better applications and services. The 3rd Generation Partnership Project 2 (3GPP2) developed Code Division Multiple Access 2000 (CDMA 2000), 1× Evolution Data Optimized (1×EVDO) and Ultra Mobile Broadband (UMB) systems. The 3rd Generation Partnership Project (3GPP) developed Wideband Code Division Multiple Access (WCDMA), High Speed Packet Access (HSPA) and Long Term Evolution (LTE) systems. The Institute of Electrical and Electronics Engineers (IEEE) developed Mobile Worldwide Interoperability for Microwave Access (WiMAX) systems. As more and more people become users of mobile communication systems and more and more services are provided over these systems, there is an increasing need for mobile communication systems with large capacity, high throughput, lower latency and better reliability.
Millimeter-Wave Mobile Broadband (MMB) system based on millimeter waves i.e. radio waves with wavelength in range of 1 millimeter (mm) to 10 mm, which corresponds to a radio frequency of 30 Gigahertz (GHz) to 300 GHz, is a candidate for next generation mobile communication technology as vast amount of spectrum is available in millimeter wave band. An MMB network consists of multiple MMB base stations (BSs) that cover a geographic area. In order to ensure good coverage, MMB base stations need to be deployed with higher density than macro-cellular base stations. In general, roughly the same site-to-site distance as microcell or pico-cell deployment in an urban environment is recommended for the MMB base stations. The transmission and/or reception in an MMB system are based on narrow beams, which suppress the interference from neighboring MMB base stations and extend the range of an MMB link. This allows significant overlap of coverage among neighboring base stations. Unlike cellular systems that partition the geographic area into cells with each cell served by one or a few base stations, the MMB base stations form a grid with a large number of nodes to which an MMB mobile station (MS) can communicate. The MMB base station grid eliminates the problem of poor link quality at the cell edge that is inherent in cellular system and enables high-quality equal grade of service (EGOS) regardless of the location of a mobile.
In order to utilize the fact that MS can detect signal from multiple BSs in MMB network, a virtual cell (or the cloud cell) is formed around the MS. A cloud cell is a virtual cell consisting of multiple BSs that serve a MS. The BSs in a cloud cell communicating with the MSs need to perform downlink (DL) Tx Beamforming, while the MSs may need to perform DL Rx Beamforming to receive DL control and data. An MS communicating with a BS in the cloud cell may need to perform uplink (UL) Tx Beamforming while the BS will perform UL Rx Beamforming to transmit UL data.
In order for MS to communicate with base stations in cloud cell an address is needed to identify the MS. For example, address is needed for Unicast resource allocation signaling transmission by BS such as Downlink and Uplink MAP wherein the address indicates to MS whether the resource allocation is for it or some other mobile station, Bandwidth Request transmission by MS wherein the address indicates to BS the identity of the MS which has transmitted the bandwidth request and for scrambling the physical layer protocol data units.
In one of the existing methods each BS maintains an independent address space and MS is assigned an address which is not used by any BS in cloud cell (CC). In this method, the cloud cell master coordinates with BSs in cloud cell to determine the address to be assigned to the MS. MS uses the assigned address to communicate with any BS in CC. This method requires coordination amongst the BSs in cloud cell. It also results in address update whenever the cloud cell is updated.
In another existing method, in order to reduce the coordination amongst the BSs in cloud cell disjoint sets of addresses are maintained by each BS. This requires careful planning so that BSs in cloud cell do not have overlapping address sets.
In another existing method, MS is assigned multiple addresses in cloud cell, one by each BS. MS uses the address specific to the BS while communicating with a BS in CC. This method requires MS to handle multiple addresses and hence results in increased complexity.
In the existing wireless communication systems wherein MS communicates with one BS, it is assigned different logical addresses to be used in different states and needs to be updated whenever the domain in which the address was assigned is crossed because of MS mobility.
Due to aforementioned reasons, it is evident that existing methods are not efficient in addressing MS's in such a cloud cell environment. Further, an efficient method of addressing the MS which reduces the air interface overhead along with reduced planning, BS coordination and complexity in wireless communication system is needed.